I have been an avid user and promotor of MindMeister since I was introduced to the program more than a year ago. My students use it in the classroom, for studying, and for collaboration on projects and material. I use it to organize lesson plans and to collaborate with students.
MindMeister just published an excellent post about using their tool for online collaboration. See the article: “Mind Mapping – Online Collaboration“. It highlights the programs abilities to organize, list, and collaborate on a multitude of topics.